Aluminum cans are widely used as containers for retail sale of beverages in individual portions. Annual sales of such cans are in the billions and consequently, over the years, their design has been refined to reduce cost and improve performance. Additional refinements have been made in the production process and equipment used for manufacturing such containers to further reduce costs and eliminate scrap and waste.
The method and apparatus of the present invention are particularly adapted for making a shell for a can lid using current single-action or double-action mechanical presses, with redesigned tooling. Presently, a shell for a beverage can lid has a center panel, a countersink, and a seaming panel, which consists of an outer seaming portion and a connecting portion, although many variations of the basic can lid can be found in use. In some arrangement of can lids, the connecting portion is almost vertical. In more recent designs of can lids, the connecting portion has been formed at more of an angle from vertical. Beverage can lids are usually formed from relatively thin sheet metal materials. The formation of a can lid shell is a metal drawing operation. If the shell is made from round blanks of sheet metal, a single-action press is used to form and shape the lid. If the lid is made from a preformed cup, a double-action press is used for completion of forming and shaping the lid.
In the effort to reduce costs and improve performance, the sheet material used to manufacture cans and lids has become progressively thinner, and the alloys used stronger. Currently, the materials have an initial thickness of 0.0088 inches or less, this thickness being projected to continue to decrease with technological developments. As the sheet material used to form lids has become thinner, the forming of can lids has become more difficult, because the thinner materials are more prone to wrinkling and cracking of the sheet material during forming. This is especially true in can lids in which the connecting portion is at a greater angle. It is not uncommon, with current materials, to use forces of up to 1100 pounds to secure such lids in the tooling during the shell forming operation, while lids with essentially vertical connecting portions may be formed using forces of approximately 400–500 pounds. The increased force required during the forming process accelerates wear on tooling, requires increased energy to generate the needed force, and requires increased support during forming to prevent distortion.
Therefore, what is needed is a method for forming can lid shells that enables better control of high strength, thin gauge material while forming can lid shells that decreases material failures, and requires a decreased load on the presses and tooling, thus prolonging the life of the equipment. Additionally, what is needed is apparatus that can achieve the desired method for forming can lid shells.